The present invention is directed generally to the field of circuit breakers, and more particularly, to a circuit breaker including a pyrotechnic element for breaking the circuit.
The circuit breakers used in various electrical systems in motor vehicles such as automobiles, trucks, buses, fixed wing aircraft, helicopters, marine vessels and the like, have conventionally employed fuse-type resistor elements that burn out when an excessive level of current passes through the element, causing a break in the circuit.
Various substitutes for such conventional fuses have also been devised, such as to permit breaking of a circuit in response to abnormal conditions (such as the collision of a vehicle) that would not necessarily create an immediate excessive current load in a fuse. For example, U.S. Pat. No. 6,194,988 to Yamaguchi et al. teaches the use of a sort of “hot plate” that is spring-biased against a relatively low melting point fuse section, with the hot plate being heated by an attached igniting device that contains a solid combustion agent; the igniting device is rapidly activated such as in the case of a collision, heating the hot plate which then melts the adjacent fuse section and (due to the spring bias) drives through the molten fuse section, cutting it out and thereby breaking the circuit. Devices such as that of the '988 patent based on melting that is induced by conducted heat, however, cannot exploit the rapidity of a pyrotechnic ignition because the process of heat conduction is quite slow in comparison to the speed of a pyrotechnic ignition. Such devices can also be relatively complex and costly.
There are also a number of recent battery cable clamp breaker devices that include a pyrotechnic device (configured to ignite in response to an abnormal condition such as a collision of the vehicle containing the device) that physically drives apart two parts of the clamp or terminal so that they are no longer electrically connected, such as in U.S. Pat. No. 5,725,399 to Albiez et al. and U.S. Pat. Nos. 5,818,121, 6,144,111, and 6,171,121 to Krappel et al. This type of device is generally capable of deploying quickly, e.g., in the case of a collision so as to reduce the chance of an electrical fire in the damaged vehicle irrespective of whether the conditions would rapidly cause a conventional fuse to blow. Yet such devices are in general a relatively complex, costly, and/or bulky way to provide the function of pyrotechnically-induced circuit breaking. Moreover, such devices do not intrinsically involve a conventional (i.e., current load-based) fuse, so if it were desired to also retain the conventional function of current load-based breaking in such a circuit breaker, a conventional fuse would need to be added as a distinct additional component, thus rendering the resulting device yet more complicated and costly.
Finally, U.S. Pat. No. 5,877,563 to Krappel et al. teaches various breaker devices in which a pyrotechnic device is used to propel a cutter(s) through a cable(s) or to unplug a connector(s). The '563 patent, however, does not teach either the direct pyrotechnic ablation of any portion of a circuit, the pyrotechnically-driven cutting of a portion of the circuit that is specially formed to be readily cut, or any kind of pyrotechnically-driven breaking of a current load-based fuse in a circuit. Thus the devices taught in the '563 patent are somewhat complicated, and none includes the function of a conventional current load-based fuse.